Communities of small mammals and small carnivores in the Teesta River Basin, Sikkim Himalaya, India

Abstract

Differences in communities of plants and animals along environmental gradients have been the basis for many ecological theories. Among the first geographical patterns to be recognized in ecology was the climatic gradient in body size of animals, later formalized as the Bergmann 's rule. Latitudinal and altitudinal gradients in species richness are other geographical patterns that have long since been recognized. The different nature of gradients and the ecological factors that cause such gradients have both been subjects of considerable debate in recent decades. Community structure in animals can also be influenced by various factors such as vegetation, biological constraints and historical factors, which may not form gradients. In this dissertation I have examined the in fluence of altitude and vegetation on communities of small mammals and small carnivores in the 11 Himalayan mountain ranges in the Indian State of Sikkim. The sharp altitudinal gradient from 230 m to 8586 m and the variety of vegetation types in this small state,. The overall goal of this study was to examine the influence of altitude and vegetation on the organizalion of the small mammal community in Sikkim Himalaya, with respect to its species richness, composition. distribution, and abundance. The specific objectives of this study were: a. To test the hypothesis that the body weight of murid rodents and shrews should respond to the sharp altitudinal gradient; b. To identify the pattern of variation in the community structure of the murid rodents and shrews along an altitudinal gradient and among different vegetation types; c. To test the hypothesis that murids and shrews differ in microhabitat use in a manner that is consistent between vegetation types; and d. To examine the influence of altitude and vegetation types on the composition and relative abundance of the small carnivore community, as well as their diet. This study was carried out in the North and South Districts of Sikkim in the Teesta River Basin, between 230 m to 3700 m altitude, from June 2003 to April 2004 and from May 2005 to December 2005